Printing web system

ABSTRACT

A web system, such as a printing web system, having reduced power consumption is disclosed. Power consumption is reduced by joining the unwind and rewind shafts of the web system together through a continuously variable transmission (CVT). The CVT allows the unwind and rewind rolls to provide torque to each other as well, allowing fewer drive motors and/or drive motors of smaller size to be used in the web system.

BACKGROUND

The present disclosure relates to web systems used in printing orcoating systems such as a printing press. In particular, the web systemsof the present disclosure have reduced power consumption, etc., due tothe use of a continuously variable transmission.

Printing web systems are used to produce high-quality reproductions, inboth black/white and in color, on paper webs traveling through thesystem at high speeds. Speeds can be as high as 2,000 feet per minute.The paper web is under tension as it travels through the system. Thistension is essential in, for example, maintaining registration of colorimages as each color is printed onto the paper web.

In a conventional web system, a web (paper or some other suitablesubstrate) travels from an unwind roll to a rewind roll. At thebeginning of the process, the unwind roll contains the entire web andthe rewind roll is empty. The web is fed through a first tensioningsystem and then enters a processing system. Inside the processingsystem, the web experiences changes in tension, for example, (i) when itmoves past various parts, for example, the print cylinder, feed rollers,angle bars, folders, etc.; (ii) as its surface properties change due to,for example, placement of ink on portions of the surface; and (iii)changing properties in the paper as it gets wet and then is dried. Afterexiting the processing system, the web is fed through a secondtensioning system and then onto the rewind roll. At the end of thisprocess, the unwind roll is empty and the web has been collected on therewind roll.

The tensioning systems are used to ensure proper unwind and uptake onthe unwind and rewind rolls, respectively, as well as to prevent the webfrom exceeding its tensile strength and breaking, which can also causeproblems such as damage to fragile print blankets and lengthy downtimein restringing the web. The difference in tension between the unwindroll and rewind roll can be used to pull the web through the processingsystem. Alternatively, another motor can be included in the processingsystem to maintain the tension in the web system.

The amount of tension present in the unwind roll can be determined bythe formula: Tension=0.5*F/(w×h), where F is the downward force appliedto the web, w is the width of the web, and h is the thickness of theweb.

In order to move the web through the web system, torque must be providedto both the unwind roll and rewind roll. Generally speaking, for eachroll a dancing roll in the tensioning system provides a force and theweb has a velocity. The surface velocities of the unwind roll and rewindroll are generally about equal to prevent the web from breaking.However, because the web is continually being unwound from the unwindroll and wound onto the rewind roll, the amount of torque which must beprovided to each roll to provide the tension changes continually.

The amount of power needed to provide the torque can be calculated usingthe formula P=F·v, where P is the power, F is the force and v is thesurface speed. It should be noted that because the radius of the rollchanges, the angular velocity of the roll also changes according to therelation v=r dθ/dt, where r is the radius of the roll and dθ/dt is theradial velocity (measured in radians/second). With a web system, thetension is set to 0.5-1.0 lbf per inch of width per milli-inch of paperthickness. For paper that is 12 milli-inches thick and 10 inches wide,the required force is 120 lbf, or about 534 newtons (N). At a webvelocity of 2 meters/sec, the required power is 1068 Nm/sec, or 1.068kW.

A motor is attached to each roll (unwind and rewind) to provide thispower. Such motors can be expensive. In addition, such motors wasteenergy because the high power levels they provide are only required whenthe weight of the roll is high.

It would be desirable to provide a web system that has reduced powerconsumption and/or reduced fixed initial installation costs.

BRIEF DESCRIPTION

The present disclosure is directed, in various embodiments, to websystems that have reduced power consumption. The web systems comprise acontinuously variable transmission.

In embodiments, a web system that provides tension with reduced powerconsumption is disclosed. The web system comprises:an unwind shaft, arewind shaft, and a processing system; a drive path running from theunwind shaft through the processing system to the rewind shaft; a drivemotor located along the drive path; and a continuously variabletransmission comprising a first shaft and a second shaft, wherein thefirst shaft is connected to the unwind shaft and the second shaft isconnected to the rewind shaft.

The continuously variable transmission can be a variable diameter pulleysystem; a toroidal transmission system; a hydrostatic transmissionsystem, or any other CVT system.

The drive motor can be located at the unwind shaft, at the rewind shaft,or along the drive path of an associated web. The drive motor can be adrive nip.

The web system may further comprise a web differential velocitymeasurement system. The web differential velocity measurement system maycomprise a dancing roll and a position sensor. Alternatively, the webdifferential velocity measurement system may comprise a stationary rolland a tension sensor. The processing system of the web system maycomprise a printing press.

In other embodiments, a method of reducing the power consumption of aweb system is also disclosed, the method comprising: providing a websystem comprising an unwind shaft, a rewind shaft, and a processingsystem; and connecting the unwind shaft and the rewind shaft to a firstshaft and a second shaft of a continuously variable transmission.

These and other non-limiting characteristics of the exemplaryembodiments of the present disclosure are more particularly describedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, which arepresented for the purpose of illustrating the exemplary embodimentsdisclosed herein and not for the purpose of limiting the same.

FIG. 1 is a diagram of a conventional web system.

FIG. 2 is a diagram of an exemplary embodiment of the web system of thepresent disclosure.

FIG. 3 is another diagram of an exemplary embodiment of the web systemof the present disclosure.

FIG. 4 is a diagram of a belt suitable for use in a variable diameterpulley system that serves as the continuously variable transmission.

FIG. 5 is a first diagram of one configuration of the variable diameterpulley system.

FIG. 6 is a second diagram of another configuration of the variablediameter pulley system.

FIG. 7 is a first diagram of one configuration of a toroidaltransmission system that serves as the continuously variabletransmission.

FIG. 8 is a second diagram of another configuration of the toroidaltransmission system.

FIG. 9 is a diagram of a hydrostatic transmission system that serves asthe continuously variable transmission.

FIG. 10 is another diagram of an exemplary embodiment of the web systemof the present disclosure.

DETAILED DESCRIPTION

A more complete understanding of the components, processes, andapparatuses disclosed herein can be obtained by reference to theaccompanying figures. These figures are merely schematic representationsbased on convenience and the ease of demonstrating the presentdevelopment and are, therefore, not intended to indicate relative sizeand dimensions of the devices or components thereof and/or to define orlimit the scope of the exemplary embodiments.

Although specific terms are used in the following description for thesake of clarity, these terms are intended to refer only to theparticular structure of the embodiments selected for illustration in thedrawings and are not intended to define or limit the scope of thedisclosure. In the drawings and the following description below, it isto be understood that like numeric designations refer to components oflike function.

FIG. 1 is a diagram showing a conventional web system 10. An unwind roll20 provides the web 30 (paper or some other suitable substrate) to therewind roll 40. The web is fed through a first tensioning system 50 andthen enters a processing system 60. Inside the processing system, theweb experiences changes in tension. After exiting the processing system60, the web is fed through a second tensioning system 70 and then ontothe rewind roll 40. At the end of this process, the unwind roll 20 isempty and the web 30 has been collected on the rewind roll 40.

In order to move the web through the web system, torque must be providedto both the unwind roll 20 and rewind roll 40. At the unwind roll 20 thedancing roll 55 provides a force F1 and the web has a velocity V1.Similarly, at the rewind roll 40 the dancing roll 75 provides a force F2and the web has a velocity V2. Again, V1 and V2 are generally equal toprevent the web from breaking.

The amount of power needed to provide the torque can be calculated usingthe formula P=F·v, where P is the power, F is the force (F1 or F2) and vis the surface speed (V1 or V2). The relation between the surface speedof the web and the angular velocity of the roll is given by v=r dθ/dt,where r is the radius of the roll and dθ/dt is the radial velocity(measured in radians/second). It should be noted that because the radiusof the roll changes, the angular velocity of the roll will also change.

The web systems of the present disclosure have reduced power consumptioncompared to the web system of FIG. 1. They achieve this reduced powerconsumption by the use of a continuously variable transmission (CVT)which is connected to both the unwind roll and the rewind roll of theweb system. This connection allows tension to be applied to the webwithout the use of motors.

FIG. 2 is a diagram showing the setup of a web system 100 of the presentdisclosure. Similar to FIG. 1, an unwind roll 110 provides a web 120,which moves along a drive path 130 through a processing system 140 andthen onto a rewind roll 150. A web differential velocity measurementsystem 160 measures the difference in the surface velocities of theunwind roll and rewind roll. The unwind roll 110 is mounted on an unwindshaft 170 and the rewind roll 150 is mounted on a rewind shaft 180. Theunwind shaft 170 and rewind shaft 180 are connected to each otherthrough a continuously variable transmission 190. As the diameters ofthe unwind roll 110 and rewind roll 150 change, the web differentialvelocity measurement system produces a signal indicative of thedifference in velocities. The signal is used in a servo control whichadjusts the transmission ratio of the continuously variable transmission190 to allocate the torques and balance the angular velocities of thetwo rolls. This allocation of torque keeps the web 120 under tension,such that power is generally needed only to make up for friction losses.Put another way, the unwind shaft 170 and rewind shaft 180 also providetorque to each other, so that torque does not need to be provided by adrive motor or the drive motor can be of a smaller size.

FIG. 3 is a diagram showing the web system 100 without the unwind rolland rewind roll. A drive path 130 is defined by the unwind shaft 170,rewind shaft 180, and processing system 140. It should be kept in mindthat the drive path 130 will move as the diameters of the unwind rolland rewind roll change.

The processing system 140 may be any system that operates on the web.For example, the processing system can be a printing press or a simplerewind operation.

Exemplary CVT systems include a variable diameter pulley system; atoroidal transmission system; and a hydrostatic transmission system.

A variable diameter pulley (VDP) system is illustrated in FIGS. 4-6. Avariable diameter pulley system comprises a first shaft 210 and a secondshaft 220. On each shaft are mounted two cones 230, 235 with apexespointing to each other to form a pulley. A belt 240, typically aV-shaped belt as shown in FIG. 4, rides in the groove formed by the twocones. The distance between the center of the pulley to where the beltmakes contact in the groove is known as the pitch radius. The distancebetween the two cones can be changed. When the cones are far apart, thebelt rides lower and the pitch radius decreases. When the cones areclose together, the belt rides higher and the pitch radius increases.The belt 240 links the two shafts 210, 220 together by transferringpower between them. Hydraulic pressure, centrifugal force or springtension can be used to create the force necessary to change the distancebetween cones. When paired together, the ratio of the pitch radius onthe first shaft to the pitch radius on the second shaft determines thegear ratio. As the two pulleys change their radii relative to oneanother, they create an infinite number of gear ratios—from low to highand everything in between. FIG. 5 illustrates a “high” gear and FIG. 6illustrates a “low” gear.

A toroidal transmission system is illustrated in FIGS. 7 and 8. Again, afirst shaft 310 and second shaft 320 are present. Attached to each shaftis a cone 330, 340 having a hyperboloid shape, arranged so the apexesface each other. Rollers 350 are placed parallel to and touching thesurfaces of the two cones. The rollers act like the belt of the VDPsystem, linking the two shafts and transferring power between them. Asthe rollers rotate in the indicated direction 360, the first shaft 310rotates in one direction 370 and the second shaft 320 rotates in theother direction 380. Tilting the rollers 350 changes the location atwhich they intersect the two cones 330, 340, creating an infinite numberof gear ratios. FIG. 7 illustrates a “high” gear and FIG. 8 illustratesa “low” gear.

A hydrostatic transmission system is illustrated in FIG. 9. Again, afirst shaft 410 and second shaft 420 are present. The first shaft 410 isconnected to a hydrostatic variable-displacement pump 430 and the secondshaft 420 is connected to a hydrostatic motor 440. The rotational motionof the first shaft 410 is converted by the hydrostatic pump 430 intofluid flow (indicated by arrow 450). The fluid travels to thehydrostatic motor 440 of the second shaft 420, which converts the fluidflow back into rotational motion. In this way, the traveling fluid actsas a power transfer linkage. The fluid is then returned to thehydrostatic pump (indicated by arrow 460).

As described above, the continuously variable transmission comprises afirst shaft and a second shaft. The first and second shafts areconnected to the unwind shaft and the rewind shaft, respectively, orvice versa.

A drive motor is still needed to impart a velocity to the web. The drivemotor can be mounted on the unwind shaft, the rewind shaft, or along thedrive path. For example, drive motor 195 is a drive nip formed by theuse of two driving rolls, such as that shown in FIG. 2. In particular,the drive motor may be of a smaller size than otherwise needed, becausethe continuously variable transmission provides tension in the web, notjust the drive motor itself.

In FIG. 3, the web differential velocity measurement system 160 is aposition measurement system. The position measurement system measuresthe integral of the difference in unwind and rewind velocity. Theposition measurement system comprises a dancing roll 162 and a positionsensor 164. The dancing roll 162 can move and applies a force F3 toprovide the tension. The position sensor 164 detects the position of thedancing roil and provides a position signal. The position signal servesas input to, for example, a servo controller 166, which provides anoutput signal to an actuator 168 that adjusts the continuously variabletransmission 190 to keep the dancing roll 162 within a predeterminedrange. Because the actuation speed is low, the actuator does not need alot of power. For example, the actuator 168 could be a lead screw drivenby a stepper motor or DC motor. In FIG. 3, the tension measurementsystem 160 is shown as being located between the rewind shaft 180 andthe processing system 140. However, the tension measurement system couldalternatively be located between the unwind shaft 170 and the processingsystem 140. In contrast to the system shown in FIG. 1, only one tensionmeasurement system is necessary because the unwind shaft 170 and rewindshaft 180 are connected through the continuously variable transmission190.

In FIG. 10, another embodiment of the web differential velocitymeasurement system 160 is shown. Instead of a dancing roll that canmove, a stationary roll 163 is present. A tension sensor 165 is attachedto the stationary roll 163 and measures the amount of tension placed onthe stationary roll, producing a tension signal. The tension signal isproportional to the integral of the difference in unwind and rewindvelocities. The tension signal is provided to an actuator 168 thatadjusts the continuously variable transmission 190 to keep the tensionon the stationary roll 163 within a predetermined range.

As a result, the web system of the present disclosure may have fewermotors than are present in conventional systems. In addition, the motorsthat are present may be of a smaller size. This allows for reduced fixedinitial installation costs and/or reduced power consumption duringoperation.

While particular embodiments have been described, alternatives,modifications, variations, improvements, and substantial equivalentsthat are or may be presently unforeseen may arise to applicants orothers skilled in the art. Accordingly, the appended claims as filed andas they may be amended are intended to embrace all such alternatives,modifications variations, improvements, and substantial equivalents.

1. A web system that provides tension with reduced power consumption,comprising: an unwind shaft, a rewind shaft, and a processing system; adrive path running from the unwind shaft through the processing systemto the rewind shaft; a drive motor located along the drive path; and acontinuously variable transmission comprising a first shaft and a secondshaft, the first shaft and second shaft being connected to each otherthrough a power transfer linkage; wherein the first shaft is connectedto the unwind shaft and the second shaft is connected to the rewindshaft.
 2. The web system of claim 1, wherein the continuously variabletransmission is a variable diameter pulley system.
 3. The web system ofclaim 1, wherein the continuously variable transmission is a toroidaltransmission system.
 4. The web system of claim 1, wherein thecontinuously variable transmission is a hydrostatic transmission system.5. The web system of claim 1, wherein the drive motor is located at theunwind shaft.
 6. The web system of claim 1, wherein the drive motor islocated at the rewind shaft.
 7. The web system of claim 1, wherein thedrive motor is a drive nip.
 8. The web system of claim 1, furthercomprising a web differential velocity measurement system.
 9. The websystem of claim 8, wherein the web differential velocity measurementsystem comprises a dancing roll and a position sensor.
 10. The websystem of claim 8, wherein the web differential velocity measurementsystem comprises a stationary roll and a tension sensor.
 11. The websystem of claim 1, wherein the processing system comprises a printingpress.
 12. A web system that provides tension with reduced powerconsumption, comprising: an unwind shaft, a rewind shaft, and aprocessing system; a drive path running from the unwind shaft throughthe processing system to the rewind shaft; a drive motor located alongthe drive path; a tension measurement system located along the drivepath; and a continuously variable transmission comprising a first shaftand a second shaft, the first shaft and second shaft being connected toeach other through a power transfer linkage; wherein the first shaft isconnected to the unwind shaft and the second shaft is connected to therewind shaft.
 13. The web system of claim 12, wherein the continuouslyvariable transmission is a variable diameter pulley system.
 14. The websystem of claim 12, wherein the continuously variable transmission is atoroidal transmission system.
 15. The web system of claim 12, whereinthe continuously variable transmission is a hydrostatic transmissionsystem.
 16. The web system of claim 12, wherein the drive motor islocated at the unwind shaft.
 17. The web system of claim 12, wherein thedrive motor is located at the rewind shaft.
 18. The web system of claim12, wherein the drive motor is a drive nip.
 19. The web system of claim12, further comprising a web differential velocity measurement system.20. A method of reducing the power consumption of a web system,comprising: providing a web system comprising an unwind shaft, a rewindshaft, and a processing system; and connecting the unwind shaft and therewind shaft to a first shaft and a second shaft of a continuouslyvariable transmission.